You can delete a master from the current edition only if it's not used by any page.

To delete a master

1.Run Fred4, and then on the Editions main tab, open an edition.

2.On the masters list, right-click one or more masters and then select Delete Selected.

3.Should the "Unable to delete a referenced master" message appear, it means the master is used on one or more pages in the current edition. Unassign the master from those pages, and then retry. Note: it is not possible to use search to find where the master is assigned - you have to browse all pages and locate it manually. The assigned master name is shown in parenthesis next to page in the Pages list, e.g. (Frontpage).